Typically, a tread pattern based on lug grooves with many edge components, for which groove area and groove depth is great is used for pneumatic tires to be used for traveling on muddy ground, snowy roads, sandy land, and the like (hereinafter referred to as “muddy ground and the like”). Such tires seek to bite into the mud, snow, sand, or the like (hereinafter referred to as “mud and the like”) on the road surface to obtain traction performance and also prevent mud and the like from forming a clog in the grooves (improve discharging performance of mud and the like) in order to improve driving performance (mud performance) on muddy ground and the like (e.g. see Japanese Unexamined Patent Application Publication No. 2011-183884A).
The technology described in Japanese Unexamined Patent Application Publication No. 2011-183884A calls particular attention to the sinking in of a region from the shoulder portion to the sidewall portion in mud and the like when traveling on muddy ground and the like, and describes opening a lug groove extending outward in the tire width direction in the shoulder portion past the shoulder portion and up to the sidewall portion, and also increasing the groove width of this lug groove as going outward in the tire width direction. With such a tire, mud performance can be further improved when traveling on muddy ground and the like due to the lug groove extending outward in the tire width direction past the shoulder portion.
However, with lug grooves shaped in this manner, discharge performance of mud and the like is obtained by increasing the groove width as going outward in the tire width direction. As such, it is more difficult for mud and the like to be compacted in the lug grooves, which leads to a problem of traction characteristics, which are generated by shear force against the mud and the like compacted in the lug groove, being insufficient. Consequently, there is a problem in that high traction characteristics cannot be obtained in cases where rapid take off is required, and particularly, in situations such as when the tire has gotten into deep muddy ground and the like.